Inline detection device for self-aligned contact defects

ABSTRACT

The present invention provides an inline detection device for self-aligned contact defects, formed in a semiconductor substrate, comprising: an active area, formed in the semiconductor substrate, comprised of a first gate having spacers on the side, at least one contact window formed between the spacers, a first contact plug formed in the first contact window, and a first contact area connecting with the first contact plug; and at least two probing pads, formed in the semiconductor substrate, comprised of a plurality of second gates formed with spacers on the side, second contact windows exposing the second gates, a second contact plug formed in the second contact window, and a second contact area connecting with the first contact area. According to the present invention, defects are detected by electrical measurement immediately following the formation of contact plugs. Moreover, conventional processes can be used for the method for fabricating the inline detection device for self-aligned contact according to the invention. The detection device is formed simultaneously with the semiconductor device without extra process or steps.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to an inline detection device for defects in semiconductor devices, and more particularly to an inline detection device for self-aligned contact defects.

[0003] 2. Description of the Prior Art

[0004] In the continuous development for integrated circuits (IC) of higher density and chips in reduced size, misalignment of various layers is a major issue. Consequently, the self-aligned contact (SAC) process has evolved to reduce the distance between elements and increase the density of elements.

[0005] However, the tolerence for defects is reduced greatly as a consequence of reduced IC size and higher density. Therefore, defects must be improved to increase yield. The lower the defect density, the higher the yield. In order to detect defects in ICs, various tests are usually conducted at specific stages.

[0006] At the moment, self-aligned contact process is conducted by etching between gates with the protection of spacers to avoid overetching. Thus, if the spacers are overetched, causing shorts, the performance of the products is severely affected and the yield is lowered. Conventional detection of defects is conducted after the formation of metal lines. According to the prior art, not only can the defects not be detected immediately following the formation of self-sligned contacts, needless waste of material and process time cannot be avoided. Therefore, the conventional detection method is far from ideal.

SUMMARY OF THE INVENTION

[0007] The object of the present invention is to solve the above-mentioned problems by providing an inline detection device for self-aligned contact defects, which is able to effectively detect defects after the formation of contact plugs.

[0008] Another object of the present invention is to provide a method for fabricating an inline detection device for self-aligned contact defects utilizing general processes to form the inline detection device simultaneously with the semiconductor device without extra process.

[0009] Another object of the present invention is to provide an inline detection device having high sensitivity and incresed detection efficiency to precisely detect defects in self-aligned contact/gates.

[0010] To achieve the above-mentioned objects, the present invention provides an inline detection device formed in a semiconductor substrate for self-aligned gate defects; the device comprising: an active area, formed in the semiconductor substrate, which is comprised of a first gate having spacers on the sides, at least one contact window formed between the spacers, a first contact plug formed in the first contact window, and a first contact area connecting with the first contact plug; and at least two probing pads, formed in the semiconductor substrate, which is comprised of a plurality of second gates formed with spacers on the side, second contact windows exposing the second gates, a second contact plug formed in the second contact window, and a second contact area connecting with the first contact area.

[0011] According to the present invention, the method for fabricating inline detection device for self-aligned contact defects comprises

[0012] (a) providing a semiconductor substrate having an active area and probing pads located on two sides of the active area;

[0013] (b) forming an island-shaped first gate having spacers on the side in the active area and a plurality of second gates having spacers on the side of the probing pad simultaneously, wherein the second gates are distributed as a matrix;

[0014] (c) implanting ions in the active area and the probing pads to form a first contact area outside the first gate in the active area and a second contact area outside of the second gate in the probing pads, followed by forming an overall oxide layer;

[0015] (d) forming at least one first contact window between the spacers of the island-shaped first gate and a plurality of second contact windows in the probing pads simultaneously, wherein the size of the second contact window is controlled so that half of the second gates located on the outer parts of the matrix are exposed; and forming first contact plugs in the first contact windows and a second contact plug in the second contact window.

[0016] In the inline detection device for self-aligned contact defects of the invention, the shape of the second gates are not limited, square or circular shapes used in the prior art can be adopted. Also, the pattern of the second gates are not limited, it can be distributed as a matrix.

[0017] In terms of material, the first contact plug and the second contact plug are either tungsten or polysilicon. The spacer is dielectric material, such as silicon nitride.

[0018] The inline detection device for self-aligned contact defects of the invention is show in FIG. 1A, wherein the active area 10 having island-shaped first gate 30 and a plurality of first contact windows 20 is divided into two parts by the island-shaped first gate 30. Two sides of the active area 10 are connected with probing pads 40, 50 respectively. In the probing pads 40 and 50, there are a second contact window 60 and a plurality of second gates 70 located at the bottom of the second contact window 60. The pattern of the island-shaped first gate 30 in the active area 10 is not limited, as long as the island-shaped gate divides the active area into two parts and they are not electrically connected. That is, the pattern shown in FIG. 1B can be adopted as well.

[0019]FIG. 2 is a cross-section of FIG. 1 along the line B-B′. In FIG. 2, 100 represents the semiconductor substrate of the active area, and 103 represents oxide. The plurality of the first contact windows 20 are located between the first gate 101, wherein spacers 102 are formed on two sides of the first gate 101. In addition, the area outside of the active area AA is a first contact region 110 formed by ion implantation, and first contact plugs 105 fill the first contact windows 20.

[0020]FIG. 3 is a cross-section along the line C-C′ in FIG. 1. In FIG. 3, 200 represents the probing pads, 203 represents oxide, 60 represents the second contact window in FIG. 1, 201 represents plurality of the second gates formed at the bottom of the second contact window 60, 202 represents the spacers formed on the sides of the second gates 201, and 210 represents a second contact region formed by ion implantation outside the area of the second gates 201. In addition, the second contact window 60 is filled by a second contact plug 204. The plurality of second gates are used to prevent damage caused by plasma when etching contact windows and to avoid not filling the contact windows completely because of the larger size of the contact windows. Moreover, when taking electrical measurements, voltage applied can be distributed evenly throughout the probing pads.

[0021] The number and the shape of the second gates in the probing pads are not restricted and can be adjusted based on the number of the first gate in the active area and the process conditions. However, in order to integrate the process, it is advantageous to have identical width for the first gate and the second gate.

[0022] According to the detection device of the invention, the active area is divided into two electrically divided parts by the island-shaped first gate, hence, if over-etching occurs in the formation of the self-aligned contact, shorts will occur. In this circumstance, by applying the two parts of the active area to ground connection and a certain voltage respectively, defects in the active area will be detected.

BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The present invention will become more fully understood from the detailed description of the preferred embodiments given hereinbelow and the accompanying drawings, given by way of illustration only and thus not intended to be limitative of the present invention.

[0024]FIG. 1A is a top view of the inline detection device of the present invention.

[0025]FIG. 1B shows another example of the pattern of the first gate in the active area of the inline detection device of the present invention.

[0026]FIG. 2 is a schematic cross-section of the in-line device along the line B-B′ in FIG. 1.

[0027]FIG. 3 is a cross-section of the in-line device along the line C-C′ in FIG. 1.

[0028]FIG. 4 shows process diagrams according to an embodiment of the invention.

PREFERRED EMBODIMENTS

[0029] FIGS. 4-7 show the process diagrams of the fabrication of the inline detection device according to an embodiment of the present invention. It is noted that the active area and the probing pads are formed simultaneously.

[0030] In FIG. 4, in order to show the simultaneous process in the active area (AA) and the probing pad (PP), a dotted line is drawn between AA and PP. An active area substrate 100 having an island-shaped first gate 101 with spacers 102 on the sides and a probing pad substrate 200 having a plurality of second gates 201 with spacers 202 on the sides are provided. Next, N⁺ ions are implanted in the active area substrate and the probing pad substrate to form first contact regions 110 and second contact regions 210. In the embodiment, the shape of the first gate 101 in the active area (AA) is used to divide the active area into two parts, and the shape of the second gate in PP is a 4×4 matrix (four gates; length by witdh). Therefore, in FIG. 4, four second gates 201 are shown to represent the cross-section of the probing pad.

[0031] In FIG. 5, overall oxide layers 103 and 203 are formed to cover the first gate 101 and the plurality of second gates 201. Therefore, as shown in FIG. 6, the oxide layers 103 and 203 are etched using the spacers 102, 202 as etching stop layer to form a number of first contact windows 20 in the active area. At the bottom of the first contact windows 20, the substrate 100 is exposed. Simultaneously, second contact windows 60 are formed in the probing pad to expose the second gates 202 with the remaining of the oxide 203 on half of the second gates 202 on the edges.

[0032] Finally, as shown in FIG. 7, the first contact windows in the active area and the second contact windows in the probing pad are filled with tungsten to form first contact plug 105 and second contact plugs 204.

[0033] One of the two probing pads of the inline detection device for self-aligned contact defects fabricated above is then earthed and the other pad is applied for a certain voltage for electrical measurement. If defects occurred in the active area, a current will be observed.

[0034] The foregoing description of the preferred embodiments of this invention has been presented for purposes of illustration and description. Obvious modifications or variations are possible in light of the above teaching. The embodiments were chosen and described to provide the best illustration of the principles of this invention and its practical application to thereby enable those skilled in the art to utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. All such modifications and variations are within the scope of the present invention as determined by the appended claims when interpreted in accordance with the breadth to which they are fairly, legally, and equitably entitled. 

What is claimed is:
 1. An inline detection device for self-aligned contact defects, formed in a semiconductor substrate, comprising: an active area, formed in the semiconductor substrate, comprised of a first gate having spacers on the side, at least one contact window formed between the spacers, a first contact plug formed in the first contact window, and a first contact area connecting with the first contact plug; and at least two probing pads, formed in the semiconductor substrate, comprised of a plurality of second gates formed with spacers on the side, second contact windows exposing the second gates, a second contact plug formed in the second contact window, and a second contact area connecting with the first contact area.
 2. The device as claimed in claim 1, wherein the first gate is island shape and divides the active area into two electrically divided parts.
 3. The device as claimed in claim 2, wherein the two probing pads connect with the two electrically divided parts of active area respectively.
 4. The device as claimed in claim 1, wherein the shape of the second contact windows is either square or circle.
 5. The device as claimed in claim 1, wherein the second gates are distributed as a matrix.
 6. The device as claimed in claim 1, wherein the first contact plug is either tungsten or polysilicon.
 7. The device as claimed in claim 1, wherein the second contact plug is either tungsten or polysilicon.
 8. The device as claimed in claim 1, wherein the first gate is polysilicon.
 9. The device as claimed in claim 1, wherein the second gate is polysilicon.
 10. The device as claimed in claim 1, wherein the spacers are dielectric materials.
 11. The device as claimed in claim 1, wherein the spacers are silicon nitride.
 12. A method for fabricating inline detection device for self-aligned contact defect, comprising: (a) providing a semiconductor substrate having an active area and probing pads located on two sides of the active area; (b) forming an island-shaped first gate having spacers on the side in the active area and a plurality of second gates having spacers on the side in the probing pad simultaneously, wherein the second gates are distributed as a matrix; (c) implanting ions in the active area and the probing pads to form a first contact area outside the first gate in the active area and a second contact area outside of the second gate in the probing pads, followed by forming an overall oxide layer; (d) forming at least one first contact window between the spacers of the island-shaped first gate and a plurality of second contact windows in the probing pads simultaneously, wherein the size of the second contact window is controlled so that half of the second gates located on the edges of the matrix are exposed; and (e) forming first contact plugs in the first contact windows and a second contact plug in the second contact window.
 13. The method as claimed in claim 12, wherein the island-shaped first gate divides the active area into two parts.
 14. The method as claimed in claim 12, wherein the first contact plug is either tungsten or polysilicon.
 15. The method as claimed in claim 12, wherein the second contact plug is either tungsten or polysilicon.
 16. The method as claimed in claim 12, wherein the first gate is polysilicon.
 17. The method as claimed in claim 12, wherein the second gate is polysilicon.
 18. The method as claimed in claim 12, wherein the spacer is dielectric materials.
 19. The method as claimed in claim 18, wherein the dielectric material is silicon nitride.
 20. The method as claimed in claim 12, wherein the implanted ions in step (c) is N⁺. 